physics of a motorbike collision - why it is so hazardous?

[Linker]

I have seen some computer animations where collisions of motorbikes are simulated. These animations are really realistic; even the dynamics of the driver is visualized exactly. When a motorbike with a given velocity collides with an obstacle, the driver flies off the motorbike and falls to the ground. Why the motorbike driver flies a certain way and why he can spin around in the air?

On which equations foundate computer animation engines that simulates such behavior?

 

What is the most hazardous factor injuring a motorbike driver? It is the speed from the motorbike or the falling on the ground? From which factors the lethality of a motorbike accident depends?

 

[Fuzzwood]

It is usually preceded by the rear of the motorbike trying to overtake the front wheel, thereby rotating around it. This gives an acceleration to the ass of the driver.

[Moontanman]

Having experienced a few motorcycle accidents, I have no answer other than they should be avoided at all costs. Wearing a helmet is the most important thing you can do to survive a motorcycle wreak...

[Sensei]

I have seen some computer animations where collisions of motorbikes are simulated. These animations are really realistic; even the dynamics of the driver is visualized exactly. When a motorbike with a given velocity collides with an obstacle, the driver flies off the motorbike and falls to the ground. Why the motorbike driver flies a certain way and why he can spin around in the air?

When bike or car accelerates to certain speed, all its particles have uniform velocity.

Once bike or car hits something and decelerates, driver or passengers maintain velocity that they had before accident, as they are not permanently attached to bike/car.

As a result they fly in air (in motorbike case), or smashes on front seats or window (in car case).

 

I have made simple animation for you to illustrate it.

 

 

At the beginning all parts of stick have equal velocity.

After hit, top part of stick is decelerated, but middle and bottom still have previous velocity.

In extreme situation stick could even be partitioned.

In simpler case, it's starting spinning.

 

On which equations foundate computer animation engines that simulates such behavior?

 

Actually it's very easy. Attach particle to different parts of object. Particle has position x,y,z velocity x,y,z acceleration ax,ay,az

And during animation particle is moved to new location frame by frame (or for more precision sub-frames like f.e. 1/1000 of second).

Collision routine is checking whether something exist or not in new location.

Movement is accepted when there is nothing in new location.

If no movement can be performed (collision), there is needed to calculate new velocity/acceleration.

 

The more particles is calculated, the slower simulation, but the more realistic is effect.

 

Every modern 3d game is using this technique.

 

What is the most hazardous factor injuring a motorbike driver?

 

Rapid deceleration of body while head still maintain velocity (or vice versa) will cause break of neck.

 

Two weeks ago I read in newspaper about women who literally lost head during such accident (ripped of from the rest of body).

 

 

[Moontanman]

I actually hit a car once and was catapulted up and over the car, me and the bike did a complete somersault and me and the 800lb motorcycle ended up in a pile. I remember with extreme clarity seeing my Saeing poly-carbonate fairing turn inside out before it exploded into thousands of shards. I put a pretty good dent in the car too...

 

Not a single image on google of that Saeing fairing... how odd..

[Arete]

I had a pretty bad crash on a motorbike when I was 19. A lady backed out of a garage right in front of me (She was running late for work, apparently), and I hit the side of the car doing about 70km/h. I was wearing a helmet, gloves, boots and riding pants.

 

Injury 1. As I pitched over the bike, my knee contacted the fairing or the side of the car and hyper-extended, rupturing my ACL and MCL, and tearing my meniscus.

 

Injury 2. I flew over the car and put my hand out as I hit the ground. I broke both my right radius and ulna, both of which protruded out the end of my elbow. I also managed to break a scaphoid in my left wrist. Having both arms in casts is about as much fun as you'd expect, especially with a blown knee.

 

Injury 3. The biggie - I landed on the top of my head and hyper-extended my neck. I suffered a hangman's fracture to my C2 vertebrae. Got lucky not to be dead.

 

In comparison with a car, a motorbike has little to no passive protection for the rider. No crumple zones, airbags, seat belts, head restraints, padded interior, etc. This means that in a crash, your body comes in contact with hard and sharp surfaces, like the road, car panels, poles, etc. In a car, there are many features designed to isolate a driver from hard objects, and to increase deceleration times. On a bike, you have none of these, so the injuries you potentially sustain are likely to be more severe. I also managed to be in a multiple rollover accident in a car as a passenger, and walked and walked away with minor cuts and bruises - my body never came in contact with a hard surface, like the pavement and the structure around me deformed and absorbed a lot of the force.

Edited June 2, 2014 by Arete

[Moontanman]

I had a pretty bad crash on a motorbike when I was 19. A lady backed out of a garage right in front of me (She was running late for work, apparently), and I hit the side of the car doing about 70km/h. I was wearing a helmet, gloves, boots and riding pants.

 

Injury 1. As I pitched over the bike, my knee contacted the fairing or the side of the car and hyper-extended, rupturing my ACL and MCL, and tearing my meniscus.

 

Injury 2. I flew over the car and put my hand out as I hit the ground. I broke both my right radius and ulna, both of which protruded out the end of my elbow. I also managed to break a scaphoid in my left wrist. Having both arms in casts is about as much fun as you'd expect, especially with a blown knee.

 

Injury 3. The biggie - I landed on the top of my head and hyper-extended my neck. I suffered a hangman's fracture to my C2 vertebrae. Got lucky not to be dead.

 

In comparison with a car, a motorbike has little to no passive protection for the rider. No crumple zones, airbags, seat belts, head restraints, padded interior, etc. This means that in a crash, your body comes in contact with hard and sharp surfaces, like the road, car panels, poles, etc. In a car, there are many features designed to isolate a driver from hard objects, and to increase deceleration times. On a bike, you have none of these, so the injuries you potentially sustain are likely to be more severe. I also managed to be in a multiple rollover accident in a car as a passenger, and walked and walked away with minor cuts and bruises - my body never came in contact with a hard surface, like the pavement and the structure around me deformed and absorbed a lot of the force.

 

 

For me, I stood the motorcycle on it's front tire just as I hit the car, ruined my helmet, but not my head, broken collar bone several ribs and a broken arm.

At the time I was more interested in what had happened to the bike...

[Ophiolite]

I walk a lot.

[imatfaal]

I walk a lot.

 

I ride my pushbike 50k a day through London - after Arete's description of his accident I am considering walking more.

 

We really are not designed for the rapid deceleration caused by contact of one part of the body with tarmac or automotive bodywork whilst the rest of the body continues at the same speed. That's the hi-speed/country-lane injury.

 

Although in built up areas, like my beloved Smoke, the main cause of cyclist/motorcyclist deaths (rather than injuries) is crushing rather than speed related. Cars, even small minis, have immense strength compared to the human body. A railing at the side of the road which would be wiped out by a car will crush a pedestrian/(motor)cyclist.

 

Terribly; another cyclist was killed in traffic in London this morning - seems no one to blame; just one of those things, caught between a lorry and hard place.

[Arete]

At the time I was more interested in what had happened to the bike...

 

That was my first thought too - I was on my pride and joy Ducati 916. Fortunately, a couple of passers by had the wherewithal to keep me still until the ambulance arrived - potentially saving my life, given I had a broken neck. Unfortunately, the bike was totaled. I was annoyed, I wasn't actually doing anything particularly dumb at the time, despite having gotten away with a lot of thing that were, admittedly with the benefit of hindsight, dumb.

 

 

I ride my pushbike 50k a day through London - after Arete's description of his accident I am considering walking more.

 

I commuted by pushbike all through grad school, I had a couple of incidents, but I would do it again. The motorbike accident really was a bit of a freak incident. The garage was right up on the street, and the car backed out quickly about 10 feet in front of me. Despite having what I thought were pretty good reflexes on the bike, I didn't even have time to process what was happening and brake - I think I hit the car with the throttle still open. Accidents happen. If they had of been around at the time, a leatt brace might have saved me to lot of pain and hospital time.

[imatfaal]

 

That was my first thought too - I was on my pride and joy Ducati 916....

 

First time I came off on my carbon road bike a passer-by found me bloodied on the floor, asked if I was ok and was a bit shocked with the response "yes I am fine - but look at that scratch"

 

 

I commuted by pushbike all through grad school, I had a couple of incidents, but I would do it again. The motorbike accident really was a bit of a freak incident. The garage was right up on the street, and the car backed out quickly about 10 feet in front of me. Despite having what I thought were pretty good reflexes on the bike, I didn't even have time to process what was happening and brake - I think I hit the car with the throttle still open. Accidents happen. If they had of been around at the time, a leatt brace might have saved me to lot of pain and hospital time.

 

I was exaggerating - in that I have no intention of stopping cycling as it is the only thing that keeps me fit - all the males in the generation before me on both sides of my family had heart attacks prior 65th birthday and it is the only cause of death so far between them. I am a fair bit older than you and thus realised a few too many years ago that my reactions are now crap - thus I try to ensure that it is never my reflexes that stand between me and an incident (although I did manage to slide into the back of a police motorbike on Embankment a few weeks ago) .

 

I keep on thinking about the idea of body armour and braces etc - not least the fact that some of them are designed to make one look like he-man under a cycling jersey. Carrying an extra couple of pounds up on your shoulders wouldn't exactly be fun though.

[Moontanman]

I don't think we are all on the same page here

 

My bike was an 1100 Yamaha Midnight special with a few mods. It was #5 in a long line of bikes starting with dirt bikes. The 1100 was my fav of all of them, most powerful in it's time, I loved the shaft drive, previously a 900 Kawasaki I had was chain drive, on what was then called a superbike, it ate chains like a child eats candy...

 

I was in a wreak on a Yamaha RD 350 once as well, a car turned in front of me, mostly just bruises but again my helmet was trashed..

[imatfaal]

I don't think we are all on the same page here

...

 

Yeah - we're on the same page; it's just that whilst you are at the top of the page and struggling to keep under 210kph I am right at the bottom desperately trying to get up to 35kph.

 

Just googled Yamaha Midnight Special - that's an awesome looking bike.

[John Cuthber]

I think the simple answer to the OP's question "What is the most hazardous factor injuring a motorbike driver?" is that you are not strapped into a padded steel box